Download Brain and Cranial Nerves

Insight:
Some cranial nerve disorders
Brain and Cranial Nerves (Ch. 15)
Human Anatomy lecture
I. Overview
(Directional terms:
rostral = toward the forehead
caudal = toward the spinal cord)
A. 3 Major parts – KNOW Fig. 15.1 & 15.2
1. Brain stem
- medulla oblongata
- pons
- midbrain
- diencephalon (many texts disagree and consider this a 4th part on its own)
2. Cerebrum
3. Cerebellum
B. Major landmarks
Cerebrum
• cerebral hemispheres separated by longitudinal fissure
• corpus callosum  thick band of connecting fibers at bottom of
longitudinal fissure
• gyrus (pl. = gyri) = ridge
• sulcus = groove
C. Protection and coverings
1. Same 3 meninges; no epidural space
2. Dura mater has 2 layers - Fig. 15.3
- venous sinuses lie between
3. 3 Extensions of dura help anchor brain (Fig. 15.3 & 15.5)
- falx cerebri- between cerebral hemisphere in longitudinal fissure
(attached to crista galli)
- falx cerebelli- between cerebellar hemispheres; superficial to vermis
- tentorium cerebelli- between cerebrum and cerebellum; in transverse fissure
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D. Cerebrospinal fluid (CSF)
1. Circulates around and within brain & spinal cord.
KNOW Fig. 15.4 & 15.5
2. a. 60% produced by choroid plexuses (capillary networks covered by
ependymal cells)in each ventricle and general ependymal lining of
ventricular system.
b. 40% produced in subarachnoid space
3. Pathway:
4. Reabsorbed by arachnoid granulations in dural sinuses
5. Functions
 CNS “blood”: exchange of gases, nutrients & wastes
 absorbs shock
 buoyant: 1500g vs. 50g!
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E. Blood supply
1. 4- prong supply through cerebral arterial circle (Review)
2. Brain capillaries less leaky = Blood-Brain Barrier (BBB)
II. Brain stem
A. Medulla oblongata  Fig. 15.6, but label Fig. 15.23
1. Continuous caudally with spinal cord, rostrally with pons
~ 3 cm
2. Anterior bulges – pyramids ( primarily tracts)
Lateral bulges – olives (primarily nuclei)
3. Functions
- conduction pathway - CNS (many descending tracts cross from left to right
at decussation of pyramids)
- nuclei for CN IX  XII
B. Pons (= “bridge”)
1. Connects medulla with midbrain; both to cerebellum
via cerebellar peduncles  Fig. 15.6b
“little feet”
2. Nuclei for CN V  VIII
C. Midbrain
1. rostral to pons; caudal to diencephalon
2. cerebral peduncles - anterior fiber tracts & nuclei
3. cerebral aqueduct (aqueduct of the midbrain) runs through
4. corpora quadrigemina (= “quadruplets”)
- superior colliculi - visual reflexes
- inferior colliculi - auditory reflexes
5. several other nuclei, including CN III and IV
D. Diencephalon – Fig. 15.11
1. Thalamus (80%)
- 2 large masses bulge medially into 3rd ventricle and laterally into lateral
ventricles
- connected by intermediate mass (like a dumbbell) that creates a hole in the
third ventricle
- many nuclei (23!)
- major function is as relay center for sensory information to cerebrum
2. Epithalamus – posterior roof
- Pineal gland - neuroendocrine organ
 “pine cone”
3. Hypothalamus - floor
More than 12 small nuclei
Infundibulum connects to pituitary gland
Functions: regulates autonomic nervous system and endocrine system
4. Third ventricle
- “donut” pierced by intermediate mass
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III. Cerebellum – KNOW Fig. 15.9
A. Structure
1. dorsal to brain stem, separated from cerebrum by transverse fissure
2. central vermis between two cerebellar hemispheres
3. flat folia instead of gyri
 “leaf”
4. white matter forms arbor vitae (= tree of life)
5. communicates with brain stem via 3 pairs of cerebellar peduncles
B. Functions (Fig. 15.10)
1. regulates voluntary, skilled movements by comparing intent with performance
2. regulates posture and balance
3. many others, including sensory & motor (only 10% of brain’s mass but 50% of
its neurons – 100 billion!)
IV. Cerebrum  Fig. 15.12
A. Structure
1. cerebral cortex - outer rind of gray matter: 2500 cm2
- grows rapidly in the fetus, forming gyri and sulci
- why is gray matter on outside of cerebral/cerebellar cortex but on inside of
spinal cord?   surface area for integration
2. some sulci separate each hemisphere into lobes (named after overlying bone)
-sketch-
Insula – deep in lateral sulcus  Fig. 15.16
3. white matter - under cortex -- Fig. 15.13
• association tracts- same hemisphere
• commissural tracts - between hemispheres: corpus callosum is major one
• projection tracts– outside cerebrum
4. basal nuclei (ganglia) – Fig. 15.16
- several large nuclei
5. limbic (= border) system – Fig. 15.15
– bilateral interconnected rings of structures (mostly gray matter) around
diencephalon
- includes hippocampus (=seahorse), site of neuron proliferation & fornix
(= arch)
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B. Functions (NRF text detail)
1. sensory areas - interpret and localize
2. motor areas - initiate muscular movement
3. association areas - emotion and intellect
4. basal nuclei - coordinate gross, automatic movements (like walking) and
muscle tone
5. limbic system - emotional behavior related to survival (pleasure, pain) and
memory (hippocampus)
V. Cranial nerves
KNOW CHART: Number, Name, Function, Attachment (NRF text detail)
- 12 pairs, part of PNS
- numbered with Roman numerals rostral caudal
- use mnemonic? p. 437
- Insight: p. 431
KNOW FIG. 15.23 -- left side labels and only IVI
- note that “midbrain” should be “hypothalamus”
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CRANIAL NERVE SUMMARY
NUMBER AND NAME
I – olfactory
II – optic
III –oculomotor
SITE OF ATTACHMENT
cerebrum
thalamus
Midbrain
FUNCTION
smell
vision
eyeball & eyelid movement,
pupil constriction, muscle
sense
eyeball movement; muscle
sense
IV – trochlear
(“pulley”)
Midbrain
V – trigeminal
(“triplets”)
V1 = ophthalmic
V2 = maxillary
V3 = mandibular
VI – abducens
Pons
chewing; muscle sense
facial sensation
Pons
VII – facial
Pons
VIII –vestibulocochlear
IX – glossopharyngeal
pons & medulla oblongata
medulla oblongata
X – vagus
(“wanderer”)
medulla oblongata
XI – accessory
(spinal accessory)
medulla oblongata
anterior gray horns, C1-C5
XII – hypoglossal
medulla oblongata
eyeball movement, muscle
sense
muscles of facial expression,
saliva & tear secretion;
taste, muscle sense
balance & hearing
saliva secretion, taste, blood
pressure regulation
visceral smooth muscle
control, digestive secretion;
visceral sensations, muscle
sense
head, neck & shoulder
movements, swallowing;
muscle sense
tongue movement (swallowing
& speech); muscle sense
NOTE:
1. Which 3 cranial nerves are primarily sensory?
2. There are no pure motor nerves because motor nerves also carry “muscle sense”
(proprioception) from the muscles they serve. However, 5 cranial nerves are primarily motor
and traditionally classified this way. Give the name & number of those 5.
3. Which 3 cranial nerves are involved in taste perception?
4. Which 3 cranial nerves are involved in eyeball movement?
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SKETCHES
I. D.
IV. A
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